Pendimethalin wastewater treatment method

Abstract

The present application relates to the technical field of pendimethalin wastewater treatment, and particularly relates to a pendimethalin wastewater treatment method, which comprises the following steps: step 1, adding ferrous oxide or ferrous hydroxide to the wastewater to adjust the pH of the wastewater to neutral; step 2, adjusting the pH of the primary filtrate to 2-5 by using inorganic acid, and adding an iron-carbon mixture with a mass ratio of 1:0.5-2 to perform a redox reaction; and step 3, introducing the secondary filtrate into 2-5 reaction kettles in series, and adding hydrogen peroxide in 1-3 portions according to a mass ratio of 15-25:1 between the hydrogen peroxide and COD. The pendimethalin wastewater treatment method can quickly reduce nitrate into nitrogen oxide or ammonia gas through the original cell effect of the iron-carbon mixture in the solution, and can efficiently and quickly treat the nitrate, and finally the iron ions and ferrous ions can generate corresponding hydroxides.

Description

Technical Field

[0001] This invention relates to the field of pendimethalin wastewater treatment technology, and more particularly to a method for treating pendimethalin wastewater. Background Technology

[0002] Pendimethalin is a selective herbicide widely used in agricultural production, effectively controlling annual grasses and broadleaf weeds. Due to its high herbicidal performance, it is produced and used extensively worldwide. Its production process involves various chemical reactions, such as nitrification, reduction, and condensation, generating significant amounts of wastewater in these stages.

[0003] Dimethoate wastewater typically contains nitric acid and various organic compounds. The nitric acid concentration in the wastewater is usually between 1% and 5%. Direct neutralization with sodium hydroxide will generate explosive sodium nitrate waste salt, requiring third-party treatment, which is costly and dangerous. Furthermore, different production batches or process adjustments may cause variations in nitric acid concentration, types, and contents of organic compounds, increasing the difficulty of treatment. Therefore, we propose a dimethoate wastewater treatment method to address these issues. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for treating dimethoate wastewater.

[0005] The method for treating dimethyl pendimethalin wastewater includes the following steps:

[0006] Step 1, pH adjustment and solid-liquid separation: Add ferrous oxide or ferrous hydroxide to the wastewater to adjust the pH to neutral, and obtain the primary filtrate after the first stage of filtration;

[0007] Step 2, Micro-electrolysis reaction treatment: Adjust the pH of the primary filtrate to 2-5 with inorganic acid, add an iron-carbon mixture with a mass ratio of 1:0.5-2 to carry out an oxidation-reduction reaction. The iron-carbon mixture is a mixture of iron powder and carbon powder. When adding the iron-carbon mixture, the mass of iron is 5%-15% of the mass of wastewater. The reaction ends when the bubbles stop. The secondary filtrate is obtained by second-stage filtration.

[0008] Step 3, Multi-stage catalytic oxidation: The secondary filtrate is introduced into 2-5 reactors connected in series. Hydrogen peroxide is added in 1-3 portions at a mass ratio of 15-25:1 (hydrogen peroxide to COD). After the reaction in the last reactor, the filtrate is discharged through a third-stage filtration.

[0009] Preferably, the volatile gases generated in step 1 are dried and then fed into a selective catalytic reduction denitrification system for treatment.

[0010] Preferably, the iron powder has a particle size of 0.1-0.5 mm, and the carbon powder has a particle size of 0.1-1 mm.

[0011] Preferably, the gas generated in step 2 is absorbed by deionized water, then dried, and finally fed into a selective catalytic reduction denitrification system for treatment.

[0012] Preferably, the inorganic acid is a hydrochloric acid or sulfuric acid solution with a mass concentration of 10%-30%, and the dosage is dynamically controlled by an online pH monitoring system.

[0013] Preferably, in step 3, hydrogen peroxide is added in a gradient mode, a reaction residence time of 30-60 minutes is set between adjacent reactors, and an ORP online monitoring instrument is set at the outlet of the last reactor to control the reaction endpoint.

[0014] Preferably, in step 3, the amount of hydrogen peroxide added to the first reactor is greater than 50% of the total amount added.

[0015] Preferably, the filtration devices used in the first-stage filtration, second-stage filtration, and third-stage filtration are plate and frame filter presses, and the filter residue from steps 1 and 3 is transported to solid waste treatment equipment for centralized treatment.

[0016] Preferably, the iron-carbon mixture described in step 2 can be recycled for at least 3 batches after being replenished with fresh iron powder, and the iron-carbon mass ratio is maintained at 1:0.5-2 during recycling.

[0017] Preferably, the filter residue in step 2 is dried and crushed, and the iron powder is removed by magnetic force and then weighed. When the mass of carbon powder is less than 30% of the mass of the remaining filter residue, the filter residue is transported to solid waste treatment equipment for processing.

[0018] The beneficial effects of this invention are:

[0019] 1. The dimethylpentylamine wastewater treatment method proposed in this invention first adjusts the pH of the wastewater to neutral using ferrous oxide or ferrous hydroxide, which can precipitate some solid waste (calcium, magnesium ions, etc.) and prevent these solid wastes from mixing into the iron-carbon mixture in step 2. When solid wastes are deposited on the surface of carbon powder, it will cause premature deactivation of the carbon powder and affect the number of times the iron-carbon mixture can be recycled. The treatment in step 1 can effectively reduce the amount of solid waste generated. At the same time, during the use of ferrous oxide or ferrous hydroxide, a small amount of nitrate ions can be reduced, and the iron ions generated by adjusting the pH can be easily removed in the subsequent step 2 (without introducing new impurities).

[0020] 2. In the dimethylpentylamine wastewater treatment method proposed in this invention, in step 2, a galvanic cell effect is generated in the solution through an iron-carbon mixture, with iron as the negative electrode and carbon as the positive electrode. This can quickly reduce nitrate ions to nitrogen oxides or ammonia, thus efficiently and rapidly treating nitrate ions. At the same time, ferric ions and ferrous ions can eventually generate corresponding hydroxides and precipitate. In step 2, the pH of the primary filtrate is first adjusted to weakly acidic using an inorganic acid. This can improve the reaction rate in step 2 and remove iron hydroxides adhering to the carbon powder surface when the iron-carbon mixture is recycled, ensuring that the carbon powder can participate in the reaction smoothly.

[0021] 3. The dimethyl pendimethalin wastewater treatment method proposed in this invention uses hydrogen peroxide to perform multi-stage catalytic oxidation of organic matter in the wastewater, which can effectively reduce the COD of the wastewater, while reducing the amount of hydrogen peroxide used and improving the treatment efficiency. Detailed Implementation

[0022] The present invention will be further explained below with reference to specific embodiments.

[0023] The method for treating dimethyl pendimethalin wastewater includes the following steps:

[0024] Step 1, pH adjustment and solid-liquid separation: Add ferrous oxide or ferrous hydroxide to the wastewater to adjust the pH to neutral, and obtain the primary filtrate after the first stage of filtration;

[0025] Step 2, Micro-electrolysis reaction treatment: Adjust the pH of the primary filtrate to 2-5 with inorganic acid, add an iron-carbon mixture with a mass ratio of 1:0.5-2 to carry out an oxidation-reduction reaction. The iron-carbon mixture is a mixture of iron powder and carbon powder. When adding the iron-carbon mixture, the mass of iron is 5%-15% of the mass of wastewater. The reaction ends when the bubbles stop. The secondary filtrate is obtained by second-stage filtration.

[0026] Step 3, Multi-stage catalytic oxidation: The secondary filtrate is introduced into 2-5 reactors connected in series. Hydrogen peroxide is added in 1-3 portions at a mass ratio of 15-25:1 (hydrogen peroxide to COD). After the reaction in the last reactor, the filtrate is discharged through a third-stage filtration.

[0027] The volatile gases generated in step 1 are dried and then fed into a selective catalytic reduction denitrification system for treatment.

[0028] The iron powder has a particle size of 0.1-0.5 mm, and the carbon powder has a particle size of 0.1-1 mm.

[0029] The gas generated in step 2 is absorbed by deionized water, then dried, and finally fed into a selective catalytic reduction denitrification system for treatment.

[0030] The inorganic acid is a hydrochloric acid or sulfuric acid solution with a mass concentration of 10-30%, and the dosage is dynamically controlled by an online pH monitoring system.

[0031] In step 3, hydrogen peroxide is added in a gradient mode, with a reaction residence time of 30-60 minutes between adjacent reactors, and an 0RP online monitoring instrument is installed at the outlet of the last reactor to control the reaction endpoint.

[0032] In step 3, the amount of hydrogen peroxide added to the first reactor is greater than 50% of the total amount added.

[0033] The filtration devices used in the first, second and third stages of filtration are plate and frame filter presses. The filter residue from steps 1 and 3 is transported to solid waste treatment equipment for centralized processing.

[0034] The iron-carbon mixture described in step 2 can be recycled for at least 3 batches after being replenished with fresh iron powder, with the iron-carbon mass ratio maintained at 1:0.5-2 during recycling.

[0035] In step 2, the filter residue is dried and crushed. After removing the iron powder by magnetic force, it is weighed. When the mass of the carbon powder is less than 30% of the mass of the remaining filter residue, the filter residue is transported to the solid waste treatment equipment for processing.

[0036] The main reaction principle in step 1 is as follows:

[0037] 3Fe 2+ +NO3 - +4H + =3Fe 3+ +NO↑+2H2O

[0038] The main reaction principle in step 2 is as follows:

[0039] 1) When the wastewater is acidic

[0040] 3Fe+8HNO3(dilute)=3Fe(NO3)2+2NO↑+4H2O;

[0041] 2) When the wastewater is neutral

[0042] 4Fe + NO s - +6H₂O=4Fe(OH)₂+NH₃↑

[0043] The technical solution of the present invention will be further described below through specific embodiments.

[0044] Example 1: Using pendimethalin wastewater from a pesticide factory as the wastewater to be treated, with an initial pH of 0.4 and an initial COD of 16721 mg / L, the treatment capacity was 2 m³ / L. 3 The specific processing steps are as follows:

[0045] Step 1, pH adjustment and solid-liquid separation: Add ferrous oxide to the wastewater to adjust the pH to neutral, and obtain the primary filtrate after the first stage of filtration;

[0046] Step 2, Micro-electrolysis reaction treatment: Adjust the pH of the primary filtrate to 5 with 10% hydrochloric acid, add an iron-carbon mixture, wherein the mass of iron powder is 200 kg and the mass of carbon powder is 100 kg, and the mass ratio of iron to carbon is 1:0.5, carry out the oxidation-reduction reaction, and take the termination of the reaction as the end point of the bubble. Then, obtain the secondary filtrate through the second-stage filtration.

[0047] Step 3, Multi-stage catalytic oxidation: The secondary filtrate is introduced into two reactors connected in series, and 502 kg of hydrogen peroxide is added in one batch. After the reaction in the last reactor, the filtrate is discharged through a third-stage filtration. The residence time in each reactor is 30 minutes.

[0048] Example 2: Using pendimethalin wastewater from a pesticide factory as the wastewater to be treated, with an initial pH of 0.4 and an initial COD of 16721 mg / L, the treatment capacity was 2 m³ / L. 3 The specific processing steps are as follows:

[0049] Step 1, pH adjustment and solid-liquid separation: Add ferrous hydroxide to the wastewater to adjust the pH to neutral, and obtain the primary filtrate after the first stage of filtration;

[0050] Step 2, Micro-electrolysis reaction treatment: Adjust the pH of the primary filtrate to 2 with 30% hydrochloric acid, add an iron-carbon mixture, wherein the mass of iron powder is 300 kg and the mass of carbon powder is 400 kg, and the mass ratio of iron to carbon is 1:2, carry out the oxidation-reduction reaction, and take the termination of the reaction as the end point of the bubble. Then, obtain the secondary filtrate through the second-stage filtration.

[0051] Step 3, Multi-stage catalytic oxidation: The secondary filtrate is introduced into 5 reactors connected in series, and 836 kg of hydrogen peroxide is added in 3 batches. The amount of hydrogen peroxide added to the first reactor is 436 kg, the amount added to the second reactor is 260 kg, and the amount added to the third reactor is 140 kg. After the reaction in the last reactor, the filtrate is discharged through the third stage filtration. The residence time in each reactor is 60 minutes.

[0052] Example 3: Using pendimethalin wastewater from a pesticide factory as the wastewater to be treated, with an initial pH of 0.4 and an initial COD of 16721 mg / L, the treatment capacity was 2 m³ / L. 3 The specific processing steps are as follows:

[0053] Step 1, pH adjustment and solid-liquid separation: Add ferrous hydroxide to the wastewater to adjust the pH to neutral, and obtain the primary filtrate after the first stage of filtration;

[0054] Step 2, Micro-electrolysis reaction treatment: Adjust the pH of the primary filtrate to 2 with 30% sulfuric acid, add an iron-carbon mixture, wherein the mass of iron powder is 200 kg and the mass of carbon powder is 200 kg, and the mass ratio of iron to carbon is 1:1, carry out the oxidation-reduction reaction, and take the termination of the reaction as the end point of the bubble. The secondary filtrate is obtained by second-stage filtration.

[0055] Step 3, Multi-stage catalytic oxidation: The secondary filtrate is introduced into three reactors connected in series, and 669 kg of hydrogen peroxide is added in two batches. The amount of hydrogen peroxide added to the first reactor is 469 kg, and the amount added to the second reactor is 200 kg. After the reaction in the last reactor, the filtrate is discharged through a third-stage filtration. The residence time in each reactor is 45 minutes.

[0056] Example 4: Using pendimethalin wastewater from a pesticide factory as the wastewater to be treated, with an initial pH of 0.4 and an initial COD of 16721 mg / L, the treatment capacity was 2 m³ / L. 3 The specific processing steps are as follows:

[0057] Step 1, pH adjustment and solid-liquid separation: Add ferrous hydroxide to the wastewater to adjust the pH to neutral, and obtain the primary filtrate after the first stage of filtration;

[0058] Step 2, Micro-electrolysis reaction treatment: Adjust the pH of the primary filtrate to 2 with 30% sulfuric acid, add an iron-carbon mixture, which is the iron-carbon mixture in Example 3 obtained by adding fresh iron powder, wherein the mass of iron powder is 200 kg, and the total mass of carbon powder and the substances adhering to the carbon powder is 296 kg. Carry out an oxidation-reduction reaction, with the reaction ending when bubbles are released. The secondary filtrate is obtained by second-stage filtration.

[0059] Step 3, Multi-stage catalytic oxidation: The secondary filtrate is introduced into three reactors connected in series, and 669 kg of hydrogen peroxide is added in two batches. The amount of hydrogen peroxide added to the first reactor is 469 kg, and the amount added to the second reactor is 200 kg. After the reaction in the last reactor, the filtrate is discharged through a third-stage filtration. The residence time in each reactor is 45 minutes.

[0060] Example 5: Using pendimethalin wastewater from a pesticide factory as the wastewater to be treated, with an initial pH of 0.1 and an initial COD of 13436 mg / L, the treatment capacity was 2 m³ / L. 3 The specific processing steps are as follows:

[0061] Step 1, pH adjustment and solid-liquid separation: Add ferrous hydroxide to the wastewater to adjust the pH to neutral, and obtain the primary filtrate after the first stage of filtration;

[0062] Step 2, Micro-electrolysis reaction treatment: Adjust the pH of the primary filtrate to 2 with 30% sulfuric acid, add an iron-carbon mixture, wherein the mass of iron powder is 100 kg and the mass of carbon powder is 100 kg, and the mass ratio of iron to carbon is 1:1, carry out the oxidation-reduction reaction, and take the termination of the reaction as the end point of the bubble. Then, obtain the secondary filtrate through the second-stage filtration.

[0063] Step 3, Multi-stage catalytic oxidation: The secondary filtrate is introduced into three reactors connected in series, and 537 kg of hydrogen peroxide is added in two batches. The amount of hydrogen peroxide added to the first reactor is 387 kg, and the amount added to the second reactor is 150 kg. After the reaction in the last reactor, the filtrate is discharged through a third-stage filtration. The residence time in each reactor is 45 minutes.

[0064]

[0065] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for treating dimethyl pendimethalin wastewater, characterized in that, Includes the following steps: Step 1, pH primary adjustment and solid-liquid separation: Add ferrous oxide or ferrous hydroxide to the dimethyl pendimethalin wastewater to adjust the pH of the wastewater to neutral, and obtain the primary filtrate after the first stage of filtration; Step 2, Micro-electrolysis reaction treatment: Adjust the pH of the primary filtrate to 2-5 with inorganic acid, add an iron-carbon mixture with an iron-carbon mass ratio of 1:0.5-2 to carry out an oxidation-reduction reaction. The iron-carbon mixture is a mixture of iron powder and carbon powder. When adding the iron-carbon mixture, the mass of iron is 5%-15% of the mass of dimethylpentylamine wastewater. The reaction ends when bubbles stop. The secondary filtrate is obtained by second-stage filtration. Step 3, Multi-stage catalytic oxidation: The secondary filtrate is introduced into 2-5 reactors connected in series. Hydrogen peroxide is added in 1-3 portions at a mass ratio of 15-25:1 to COD. After the reaction in the last reactor, the filtrate is discharged through a third-stage filtration. The iron powder has a particle size of 0.1-0.5 mm, and the carbon powder has a particle size of 0.1-1 mm. The iron-carbon mixture described in step 2 is recycled for at least 3 batches after being replenished with fresh iron powder, and the iron-carbon mass ratio is maintained at 1:0.5-2 during recycling. In step 2, the filter residue is dried and crushed. After removing the iron powder by magnetic force, it is weighed. When the mass of the carbon powder is less than 30% of the mass of the remaining filter residue, the filter residue is transported to the solid waste treatment equipment for processing.

2. The method for treating dimethoate wastewater according to claim 1, characterized in that, The volatile gases generated in step 1 are dried and then fed into a selective catalytic reduction denitrification system for treatment.

3. The method for treating dimethoate wastewater according to claim 1, characterized in that, The gas generated in step 2 is absorbed by deionized water, then dried, and finally fed into a selective catalytic reduction denitrification system for treatment.

4. The method for treating dimethoate wastewater according to claim 1, characterized in that, The inorganic acid is a hydrochloric acid or sulfuric acid solution with a mass concentration of 10%-30%, and the dosage is dynamically controlled by an online pH monitoring system.

5. The method for treating dimethoate wastewater according to claim 1, characterized in that, In step 3, hydrogen peroxide is added in a gradient mode, with a reaction residence time of 30-60 minutes between adjacent reactors, and an ORP online monitoring device is installed at the outlet of the last reactor to control the reaction endpoint.

6. The method for treating dimethoate wastewater according to claim 5, characterized in that, In step 3, the amount of hydrogen peroxide added to the first reactor is greater than 50% of the total amount added.

7. The method for treating dimethoate wastewater according to claim 1, characterized in that, The filtration devices used in the first, second and third stages of filtration are plate and frame filter presses. The filter residue from steps 1 and 3 is transported to solid waste treatment equipment for centralized processing.

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